Method of and apparatus for thermochemically removing metal from ferrous metal bodies



E. P. JONES TUS July 14, 1942. 2,289,968 FOR THERMO-CHEMICALLY REMO ERROUS METAL BODIES Filed April 2, 1940 vme 2 Sheets-Shet 1 METHOD OF AND APPARA METAL FROM F IgYERETT P. JONES TTORNEY E P. JONES 2,289,968

OVING July 14, 1942.

METHOD OF AND APPARATUS FOR THERMO-CHEMICALLY- REM METAL FROM FERROUS METAL BODIES I 1 2 Sheets-Sheet 2 Filed April 2, 1940 INVEI'QTOR EgERETT R JONES ATTORNEY Patented July 14, 1942 UNITED STATES PATENT OFFICE 2-,2s9,9ea

Everett P. Jones, Elizabeth, N. 1., asslrnor to The Linde Air Products Company, a corporation of MOCHEMIOALLY Ohio ApplicationApril 2, 1940, Serial No. 321,444

N -14 Claims. This invention relates to a method of and apparatus for thermo-chemically removing metal from ferrous metal bodies, and more particularly to a method and apparatus for'rapidly severing ferrous metal bars, especially round bars, with a cutting blowpipe.

Heretofore, it has been the practice to remove metal from ferrous metal bodies with a blowpipe having a nozzle provided with a central orifice producing an .oxidizing gas stream of bars with a customary cutting blowpipe. For cutting, round bars the blowpipe is positioned with its longitudinal axis in a plane normal to the longitudinal axis of the bar. The axis of suitable character which reacts with. or consumes portions of metal of the body against which vthe stream is projected which portions must be at an ignition temperature. In addition to the oxidizing gas orifice it is customary to provide in the nozzle, separate, annularly positioned, mixed gas passages having orifices adjacent the oxidizing gas orifice for producing one or more heating flames. Means are customarily provided for separately controlling the flow of oxidizing gas to the cutting orifice'and the flow of an oxidizing gas and a fuel gas to the heating flame orifices of the nozzle.

Before steel can be cut or surface metal be removed by thermo-chemical' reaction with oxygen, at least a small area of the metal to be removed must' be heated to the kindling temperature which is approximately 2300 F. For

such preheating the mixed gases forming preheating flames are turned on first and the flames are projected. against the surface of the work until an area at the starting point is sufficiently heated. Such preheating requires an appreciable period of time with the customary forms of nozzles. When the preheat is obtained, the oxidizing gas is turned on and the blowpipe is moved along the surface of the work to form a kerf or a groove, as the case may be. During such movement it isfound advantageous to continue the heating flames.. The preheating flame necessary to accompany the oxygen stream, for optimum efficiency in the consumption of gases. and rate .of cutting is relatively small. Therefore, if the blowpipe nozzle is designed to provide the most desirable size and intensity of preheatflame for carrying the cut, the flame will be relatively small and the time of preheating before starting the cut will be relatively long. If the preheating flame of the nozzle is made and will result in excess consumption of gas and in cutting may cause an excessive melting down of the upper edges of the kerf.

the blowpipe nozzle is generally also maintained vertical or substantially vertical. Thus, when starting the cut. the preheating flames will not be normal to the surface at the startin point and therefore the rate of heat transfer from the flame to the work surface is relatively low and the time required for heating the spot to the kindling temperature is further increased. It is often the case that the preheating period isas long or longer than the actual cutting period.

When manually cutting such bars, the operator 7 can tilt the torch so that the flames are normal to the surface and when an ignitionis obtained the blowpipe nozzle may be tilted back to the desired vertical position for making the out. However,

in cutting round bars with a machine propelled cutting torch, the torch usually is fixed in a'vertical position. Attempts have been'made to reduce the time of preheating to obtain an ignition by inserting a small portion of a ferrous metal rod in the heating flames and using the molten metal produced'to obtain rapid ignition. The preheating period' can be greatly reduced by 'such method. However, the deposit of molten metal may interfere with the oxygen stream so as to cause a gouge at the starting portion of the cut. The kerf produced will have a nick in the corner and therefore such cutting method will be unsatisfactory except for rough work.

A principal object of the present invention is to provide a method and apparatus for thermochemically removing metal from ferrous metal bodies which shall be rapid and eflicient and economical to use.

Other objects of the invention are to provide with increasing economy in the consumption of gases by employing only a relatively small heating flame during the metal removing step, and

by employing a relatively high intensity preheating flame only during the preheating step; to provide an apparatus for carrying out such method of removing metal which includes a nozzle for producing high-intensity preheating flames cooperating with a relatively lowin'tensity heating flame'ot the metal removing nozzle; to provide suitable means for controlling a Further difllculties result when cutting round pp of gases to the resp ve metal r m vi nozzle and the high-intensity preheating nozzle; to provide a blowpipe apparatus including a nozzle producing a'high-intensity preheating flame; and to provide a blowpipe apparatus which will efliciently and rapidly sever ferrous.

The nozzle N ismaintained a substantially con-f stant distance from the surface of the work W by a pair of guide rollers I4 that, engage the Fig. 2 ma diagrammatic view-on an enlarged scale showing the relation between the cutting,

blowpipe and auxiliary preheating blowpipe with respect to the surface of the bar to be cut;

Fig. 3 is a longitudinalsectional view on an enlarged scale of a preferred form of high-intensity preheating nozzle;

Fig. 4 is an end view of the nozzle shown in- Fig. 3;

Fig. 5 is a longitudinal sectional view of a hand-operated blowpipe embodying the principles of the invention; and

Fig. 6 is a view of a transverse section taken on the-line fi-f-B of Fig. 5. k

In the preferred form of this invention a highintensity auxiliarylpreheating nozzle is positioned at an angle with respect .to and adjacent to a cutting nozzle which may be of the customary type or which preferably is arranged to provide a relatively low heating flame. The auxiliary preheating nozzle is arranged to project a concentratedheating flame substantially normally against thespot of thesurface to which the heating flames of the cutting nozzle are directed substantially tangentially or at an acute angle. To make a cut the heating flame of the cutting nozzle is preferably ignited first, the blowpipe moved to the desired starting position, the gases are then supplied to the heating flame nozzle and the-heating flames of both nozzles will be concentratedat the starting spot of the work surface. .After a veryshort interval of time, the ignition temperature will be reached and the cutting oxygen will be turned on. Simultaneously with the turning on of the cutting oxygen to initiate the cutting reaction, the gases supplied to the auxiliary preheating nozzle will be shut off. The. cutting nozzle will then be moved relatively along the work surface to produce .the desired cut. When cutting a round bar the angular position of the auxiliary preheating nozzle is preferably arranged so that the highintensity preheating flame will impinge substantially normally against the surface of the bar.

Referring to the drawings, and particularly to Figs. 1 and 2, a cutting blowpipe B is moved 6 mechanically with respect. to a bar W'which is to be severed. The machine shown for moving the blowpipecomprises a boom R at the end of which-is supported the blowpipe B in a substantially vertical position above the work W. The 5,

boom R extends transversely of the work W and is rockably supported on top of a carriage C, the carriage C being motor driven and moving'along a hormontal track T which may be supported on the floor in a position transverse to the axis of the work W and lower than such axis. The car-' riage .C is provided with a gear-shift lever I II which, when shifted forward, engages the motor M in thecarriage C with the wheels H of the carriage to move the carriage in the forward disurface and are mounted at the lower ends of downwardly projecting arms I5 at the end of the boom R.

For providing a high-intensity preheating flame there is also mounted adjacent the blow,- pipe end of the boom R an auxiliary blowpipe H. The blowpipe H is adjustably mounted on a projection l6 secured to the boom R and has a holder il' arranged to provide longitudinal adjustment of the'blow'pipe H. The blowpipe H is positioned such that its nozzle 3 is adjacent to the nozzle N and the main axis of the nozzle feds directed to intersect the work surface substantially at the point of intersection of the axis of the nozzle N with the'work surface. The axis of the nozzle I8 is preferably more nearly normal to the portion of the work surface impinged than the axis of the nozzle N.

It is known that the rate of heat transfer from a high-velocity flame to a work surface is more rapid than the rate of heat transfer when customarily low-velocity flames are employed. It is preferable, therefore, but not essential in carrying out the method of this invention, to employ an auxiliary preheating nozzle'which will provide a heating flame 011 relatively high velocity and sage 22 therethrough. In the body portion 20 is an enlarged chamber 23 and through the tip 2! there are a plurality of passages 24 conecting the chamber 23 to a coresponding number of orifices 25. In the preferred embodiment as shown in .Fig. 4, four orifices, 25 and passages 24 are employe'd. The passages 24 preferably converge toward the orifices and the orifices 25 preferably converge toward the main axis of the nozzle in order to produce a group of extra long, highvelocity preheating fiamesvthat converge toward a point. The inner cones of the flames do not extend quite to the point of convergence and the nozzle is so positioned that the point of convergence is approximately at the point on the sur- 0 face of the bar intersected by the axis of the main nozzle N. The blowpipe H may be of the customary type adapted to mix oxidizing and fuel gas and pass the mixtiire 'to the nozzle l8 To produce the desired high-intensity conver-" gent heating flames, the gases be supplied to the'noz'zle l8 at the proper pressure and volume. The proportion of the-gases is adjusted by valves 26 and 21 at the upper end of the blow-. pipe H. Similar valves for regulating the-supply .1 gases to thecutting blowpipe B in the customary manner are provided at 28, there being three valves, one for heating oxygen, the second.

for fuel gas, and the third for cutting oxygen.

Suitable means for controlling the supply of gases in the proper sequence to the blowpipes B and H is provided. On the rear portion of the boom R are mounted three sets of lever-operated the flow of fuel gas from a supply connection 34 to a discharge conduit 35. The other valve element in valve 30 controls the flow of oxidizing gas from the supply connection 36 to the'discharge conduit 31. Conduits 35 and 31, respectively, are supported along the boom R and connect with the respective fuel gas and heating oxygen inlets of blowpipe B indicated at 35' and 31', respectively. Branch conduits 38 and 39 are connected between conduits 35 and 31 to valve elements in the valve 32 which has an operating handle 40. The valve elements in valve 32 discharge fuel gas and heating oxygen, respectively, through conduits 4| and 42 which connect with the inlet connections of the blow-pipe H at 4| and Valve 3| has a, single valve element therein which controls the flow of cutting oxygen from a supply connection 43 to a discharge conduit 44 that is supported along boom R and connects with the upper end of the blowpipe B. Valve 3| has an operating handle 45 that is preferably connected with valve handle 45 of valve 32 by a link 46 so that the valves will operate simultaneously. Valves 3| and 32 are so arranged that when the handles 45 and 4|] are rearwardly directed in the position shown, the valve element in valve 3| will be closed, while the valve elements in valve 32 will be open, and vice versa.

In operation, it will be assumed that the work W is horizontally positioned ona suitable support S; that the height of the boom R. has been adjusted so that the end of the blowpipe nozzle N will be 'at the desired level slightly higher than the axis of the work W; that the valves 28 i have been properly adjusted so that when the gases are flowing the preheating flame of the desired relatively low intensitywill be produced by nozzle N; that the valves 26 and 21 of the blowpipe H are adjusted so that when the gases are flowing the nozzle l8 will produce a relatively large high-intensitypreheating flame; that the blowpipe nozzle I8 is properly positioned as shown with respect to the nozzle N; that the motor M of the carriage C is energized; and the lever i0 is in the neutral vertical position. The operator will position the machine along the track T until the rollers l4 engage the surface of the bar W. The operator will then move the handle 33 forward thus supplying oxidizing gas and fuel gas directly to the blowpipe B and also to the blowpipe H through the open valve elements in valve 32. If the work W is sufficiently heated, for example, if it is at a rolling temperature, the gases on contacting with the surface of the work will be ignited. If the work W is not sumciently heated, other means, such as a pilot flame may be provided for effecting ignition. When the operator observes that the work has been heated to an ignition temperature, or by previous experience awaits for the relatively short interval of time which will provide an-adequate preheat, theoperator will move valve handle 45 forward thus opening the valve element in valve 3| to'supply cutting oxygen to the cutting orifice of the nozzle N. At the same time valve handle 40 will be shifted forward, thus closing thevalve elements.

in the valve 32 which shuts off the gas supplied to the blowpipe H. The valve handle 33 is left carried transversely across the work W and maintained at a substantiall constant distance from the surface by the rollers l4. When the kerf is completed the operator will pull levers 33, 45, and I0 rearwardly thus shutting off all the gases and causing the carriageC to reverse and retractthe blowpipe, If desired, the carriage C may be pulled back manually by putting the lever In in the vertical or neutral position.

When cutting cold, round, steel bars with the customary machine cutting torch, it has been found that the preheating time will range from about 25 seconds for 4 inch diameter bars to 120 seconds for 8 inch diameter bars. However, by employing the auxiliary high-intensity preheating nozzle i8, all other conditions being the same, the preheating time is reduced to approximately 4 to 6 seconds, depending on the diameter of the bar.

The principles of the invention may also be employed in a hand-operated blowpipe which may be of a type suitable for kerf cutting or of a type suitable for removing surface metal, such as deseaming, depending mainly upon the character of the nozzle N employed. The blowpipe has the customary nozzle N which is secured to the blowpipe head 48, the oxygen orifice O of the nozzle N being supplied with cutting oxygen through a passage 49 that is controlled by a, cutting valve 50. The cutting oxygen is supplied to the valve 50 through a passage 5| leading from a connection 52 at the rear of the'blowpipe. The mixed heating gases are supplied to the heating gas passages P of the nozzle N through a passage 53 which receives the gases from a mixer element 54 of a type which is customarily employed. Oxidizing gas is sup'pliedto the mixer 54 by a passage 55 controlled by a valve 56 interposed between the passage 55 and the connection 52. supplied from a connection 51 through a valve 58 and a passage 59. The above-described elements of the blowpipe shown in Fig. 5 are those so that the axes of the two nozzles will intersect at a point approximately at the level of the work surface. To permit close nozzle spacing, the tip 2| of the nozzle I8 is cut away on one side as shown at 2| in Fig. 4, and the cut-away portion is placed adjacent the nozzle N. The nozzle I8 is secured to a. head 60 which may be fastened to the head 48 by suitable means such as by providing a pair of extensions 6| on either side of the head 48 and securing them by a bolt 6| passing through both. extensions and the head 43. The head 60 is connected with the body of the blowpipe by a mixing Lube 62whichreceives mixed gas from a mixer 83 in the body of the blowpipe. The mixer 63 may also be of the customary type and similar to the mixer 54 except that the gas passages therethrough are preferably larger in order to provide a greater flow of mixed gas.

Fuel gas is To control the supply of oxidizing and fuel gas to the mixer 63 at the proper time, two control valves are provided. The fuelgas supply is controlled by a valve 64 having upper and lower valve elements both of which are seatable alternately on a valve seat 55 disposed between them. The valve seat 65 is retained in place against a shoulder by the sleeve-like extension of a valve cap 66 through which the stem 61 of the valve passes. If desired, a suitable packing may be arranged about the valve stem 61 in the cap 66 to prevent leakage of gas when the valve is opened. For controlling the flow of heating oxygen to the mixer 63 a similar valve 64 is provided. The chamber over the valve seat 65 is connected by a passage 58 with the fuel gas connection 51 and the chamber below the valve seat 65 is connected with thespace around the mixer 63 by a passage 69. Similarly, the cham ber above the valve seat 65' is connected with the oxidizing gas inlet passage 5lby a passage I0, and the chamber below the valve seat 65' is connected with the passage through the mixer 63 by a passage H. The valve stems 61 and 61 are arranged to contact with a cross bar 12 secured to the ends of a pair of vertical rods 13. The rods 13 pass slidably through projections 14 of the body of the blowpipe and springs '15 are provided acting between the bar 12 and the projections 14 to urge the rods 13 downwardly. The upper ends of the rods 13 are connected by a cross bar 16 which has a central hole therethrough through which the stem of the cutting valve 50 passes. A head 11 is secured to the end of the stem of valve 50, in order that the valve 50 maybe opened when the cross bar 16 moves upwardly.

To operate the valves, a hand lever 18 is pivotally secured at 19 to the body of the blowpipe and passes'under the bar I2. having a portion 80 contacting with the cross bar 12. Thus, when the lever 18 is pressed upwardly halfway it will force the bar I2 upwardly against the springs 15. This will press the valve stems 51 and 61' upwardly sufliciently to unseat the upper valve elements of the valves 64 and 64' from the valve seats 65 and 65 and thus permit gas to flow through the valves to the mixer 63, the mixed gas then discharging from the nozzle l8. Further upward movement of the lever 18 will press the lower valve elements of the valves 54 and 64' against the valve seats 65 and 65' to shut off the gas supply of nozzle l8, and at the same time the cross bar 16 will contact with and lift the head 11 to open the cutting valve 50. The gas flow to the auxiliary nozzle l8 will thus be shut off when the cutting valve 50'is open and operation of the blowpipe will thus be quite convenient. The oxygen andfuel-gas supply hoses will be connected to connections 52 and 51, respectively.

With the gases supplied at the proper pressure the valves 56 and 58 are adjusted to supply oxygen and fuel gas to the mixer 54 in the proper proportion to provide a normal relatively low heating flame to issue from the heating flame orifices P of the nozzle N. With the proper pressure of oxygen and fuel gas, theproportions of the mixer 63 are such that the desired highintensity heating flame will issue from the nozzle l8 when the valves and 64' are open. Thus, to start a cut the operator directs the nozzles N .and I8 at the spot where the kerf is to begin,

and having ignited the heating flames issuing.

from the nozzle N the operator will depress the lever 18 part way to start the flow of gas to the high-intensity heating nozzle [8. After'a very short interval of time the operator presses the handle I8 all the way and this action will open the cutting valve 50 and shut off the supply of heating gas to the nozzle l8. The operator then begins moving the blowpipe nozzle N along the surface of the work to remove surface metal or to cut a kerf according to the type of nozzle being employed. It will be seen that when using the present method of cutting steel bars and particularly cold, round, steel bars there will be no undesirable gouging at the start of a cut and it has been observed that after the out has been completed the only way that the position of the start of such out can be ascertained is by the fact that the starting portion of the cut appears slightly smoother than the rest of the cut.

It will be understood, that fuel gas other than those skilled in the art. Certain features of the invention may be used independently of the others and other uses of the nozzle may be found without departing from the spirit and scope of the invention as defined in the claims.

I claim:

1. A method ofsevering a ferrous metal bar which comprises directing a relatively low-intensity heating flame substantially tangentially against a curved. surface portion at one side of the bar; directing against said surface portion a separate relatively high-intensity heating flame, said high-intensity heating flame being disposed at an angle to the direction of flow of said low-intensity heating flame, and in a direction substantially normal to said surface portion; when said surface portion reaches an ignition temperature, entirely interrupting said high-intensity heating flame and simultaneously applying a. stream of oxidizing gas against said heated surface portion; continuing said low-intensity heating flame; and simultaneously moving said oxidizing gas stream and said low-intensity heating flame transversely across said bar to form a kerf therethrough.

2. A method of removing metal from a ferrous metal body which comprises applying at least one low-intensity heating flame at an acute angle against a surface portion of the metal to be removed; applying substantially normally against said surface portion a plurality of separate relatively high-intensity convergent heating flames,

said high-intensity heating flames converging to-. ward the same area of said surface portion and heated surface portion; and simultaneously moving said oxidizing gas stream and said low-intensity heating flame along the surface of said body for removing "portions of metal therefrom.

- 3. A method of severing a round ferrous metal bar supported horizontally which comprises directing a relatively low-intensity heating flame downwardly and substantially tangentially and said low-intensityheating flame and transversely across said bar;

.tinue the which said auxiliary against a curved surface portion 'at one side of the bar; directing substantially normally-against said surface portion a separate relatively highintensity heating flame, said high-intensity heatdirected substantially in the plane of the cut to be made and at an angle to the direction of flow of saidlow-intensity heating flame; when said surface portion reaches an ignition temperature, entirely interrupting said high-- intensity heating flame and simultaneously ap-, plying a stream of oxidizing gas downwardly against said heated-surface portion; continuing said low-intensity heating flame; and simultaneously moving said oxidizing gas stream tranversely across said bar while maintaining said stream in said plane to form a kerf stantially free from undesirable gouges.

4. Apparatus for severing a ferrous metal bar which comprises a cutting blowpipe adapted to apply a low-intensity heating flame and a verting valve controlling said oxidizing gas passage;

through said bar subtical stream of cutting oxygen initially against a lateral surface portion of said bar; mechanism for supporting and moving said blowpipe above an auxiliary blowpipe adapted to produce a separate relatively high-intensity heating flame, said auxiliary blowpipe being disposed adjacent said cutting blowpipe and positioned to direct said high-intensity heating flame substantially normally against the lateral surface portion impinged by said low-intensity heating flame; and valve means for controlling the supply of mixed gas to said cutting blowpipe and to said auxiliary blowpipe and the supply of cutting oxygen to said cutting blowpipe, said valve means being operable to supply said heatiig gas to both blowpipes and to discon- Few of said heating gas only to the auxiliary blowpipe when supplying cutting oxygen to said cutting blowpipe.

5. Blowpipe apparatus according to claim 4 in blowpipe is provided with nozzle me convergent high-velocity highinten'sity heating flames.

6. Blowprpeapparatus according to claim 4 in which said valve means includes conduit means for conducting cutting oxygen to said cutting blowpipe; a valve having an operating element controlling said cutting oxygen conduit; a duplex valve having operating elements controlling the supply of oxidizing gas and fuel gas to said aux iliary blowpipe; means interconnecting the operating element of said cutting oxygen valve with the operating elements of said duplex valve for closing said duplex valve when said cutting valve is opened; and a second duplex valve operative to control the supply of oxidizing gas and fuel gas to both said cutting blowpipe and said firstmentioned duplex valve.

'7. Apparatus for removing metal from a ferrous metal body which means for applying a heating flame substantially tangentially against a portion of the surface of said body and for applying an' oxidizing gas stream against said surface portion; an auxiliary nozzle mounted closely adjacent to said main nozzle, said auxiliary nozzle being adapted to apply a relatively high-intensity heating flame substantially normally to the surface portion impinged by said main nozzle; conduit means for supplying a mixed fuel and oxidizing gas to the heating flame means of said main nozzle; conduit means for supplying oxidizing gas to the oxidizing-gas passage of said main nozzle; a cutquickly the i said auxiliary nozzle and means for supplying mixed oxidizing and fuel gastosaid auxiliary nozzle; and valve means controlling the supply of oxidizing and fuel gas to operable to interrupt quickly the supply of said gases thereto substantially simultaneously. with the opening of said cutting valve.

8. Apparatus for removing metal from a ferrous metal body which comprises main nozzle means for applyinga heating flame against a portion of the surface of said body and for applying an oxidizing gas stream at an acute angle against said surface portion; an auxiliary nozzle mounted closely adjacent to said main nozzle, said auxiliary nozzle being adapted to apply a relatively high-intensity heating flame substantially normally to the surface portion impinged by said main nozzle; conduit means for supplying a mixed fuel and oxidizing gas to the heating flame means of said main nozzle; conduit means for supplying oxidizing gas to-the oxidizing-gas passage of said main nozzle; a cutting valve controlling said oxidizing gas passage; means for supplying mixed oxidizing and fuel gas to said a, iliary nozzle; and valve means controlling the supply of oxidizing and fuel gas to d auxiliary nozzle and operable to interrupt supply of said gases thereto independently of the supply of mixed fuel and oxidizing gas to the heating flame means of said main nozzle.

s constructed and arranged for producing a group of comprises main nozzle plying a heating flame to 9. Blowpipe apparatus for removing metal from a ferrous metal body which comprises a main'nozzle having an axial cutting oxygen oriflce therethrough and heating flame orifices adjacent to'said cutting orifice; an auxiliary nozzle mounted closely adjacent to and at an angle to said main nozzle, said. auxiliary nozzle being constructed to apply a high-intensity heating flame substantially normally against the surface portion of the body initially impinged substantially tangentially by oxygen discharged by said main nozzle; conduit means supplying mixed fuel and oxidizing gas to the heating flame orifices of said mainnozzle; conduit means supplying cutting oxygen to the cutting oxygen orifice of said main nozzle; a cutting valve controlling flow through said cutting oxygen conduit; a mixer for mixing oxidizing gas and fuel gas and supplying such mixed gas to said auxiliary nozzle; a pair of according to claim 9 from a metal body which comprises means for projecting a stream of oxygen at an acute angle against a surface of such body; means for apthe surface area impinged by said cutting oxygen; means for applying an auxiliary high-velocity heating flame sub stantially normally against said surface area; passage means supplying cutting oxygen to said cutting oxygen stream; a cutting valve controlling said cutting oxygen passage; means for supis provided with a plying mixed fuel and oxidizing gas to tiveiy low heating flame; a mixer for mixing oxihas reached its ignition temperature for thermochemical reaction with said 

